Conventionally, there is an air-conditioning apparatus that can control a dew point temperature of an outlet air. In such an air-conditioning apparatus, a dew point temperature detector or a humidity sensor are generally installed at an outlet to control the dew point temperature of the outlet air to be constant. As such, “a clean room using a direct expansion heat exchanger, in which the dew point temperature of the brought-in outer air is adjusted by the rotation frequency control of a compressor in the heat pump apparatus so that a detected value of a dew point sensor installed at an air cooler side is within a predetermined range” is proposed. (For example, refer to Patent Document 1)